The Sahara Desert makes up what percentage of Africa?

Africa has eight major physical regions: the Sahara, the Sahel, the Ethiopian Highlands, the savanna, the Swahili Coast, the rainforest, the African Great Lakes, and southern Africa. Some of these regions cover large bands of the continent, such as the Sahara and Sahel, while others are isolated areas, such as the Ethiopian Highlands and the Great Lakes. The Sahara is the world's largest hot desert, covering 8.5 million square kilometers (3.3 million square miles), about the size of the South American country of Brazil. Defining Africa's northern bulge, the Sahara makes up 25% of the continent.

Source: National Geographic